Single Op-Amp Current Measurement for Motor Torque Estimation
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Solution Overview
Problem
Conventional current measuring apparatuses require two operational amplifiers, increasing the cost of measuring current flowing in motors.
Innovation Solution
A current measuring apparatus using a single operational amplifier with a detection unit, smoothing unit, amplification unit, input unit, storage unit, acquisition unit, and calculation unit to estimate load torque by calculating the difference between voltages when the motor is stopped and rotating, allowing for cost-effective current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two operational amplifiers are used to measure current, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of two operational amplifiers into a single operational amplifier by combining the smoothing operation and current measurement functions that were previously performed by separate amplifiers. This reduction in component count directly addresses the technical contradiction by maintaining measurement precision while reducing device complexity and cost.
Solution Approach 2:
The single operational amplifier in the patent performs multiple functions: it conducts smoothing operations on the current signal and simultaneously performs measurement operations. This multi-functionality allows the system to achieve the same measurement precision as dual-amplifier systems while using fewer components, thereby resolving the contradiction between precision and complexity.
2Measurement precision
If two operational amplifiers are used for current measurement, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
By merging the smoothing and measurement functions into a single operational amplifier, the patent reduces the bill of materials and assembly requirements, directly lowering manufacturing cost while preserving measurement accuracy through the integrated design.
Solution Approach 2:
The patent uses a single operational amplifier to replicate the combined functionality of two separate amplifiers, achieving the same measurement accuracy at lower cost by eliminating redundant components and simplifying the manufacturing process.
3Device complexity
If a single operational amplifier is used, then device complexity and cost are reduced, but measurement precision may deteriorate
Solution Approach 1:
The single operational amplifier is designed to perform both smoothing and measurement operations, ensuring that measurement precision is maintained despite the reduction in component count. The multi-functional design prevents precision deterioration by integrating critical functions within the single amplifier.
Solution Approach 2:
The patent modifies the operating parameters and configuration of the single operational amplifier to optimize its performance for dual functions, ensuring that measurement precision requirements are met while using fewer components. This parameter optimization resolves the potential precision loss from using a single amplifier.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and cost-effective measurement of current flowing in motors by eliminating the need for two operational amplifiers, reducing the overall cost and complexity of the system.
Implementation Method 1
an amplification unit including a first input terminal at which the second signal is input, a second input terminal coupled to a first resistor and a second resistor by which an amplification factor is defined, an output terminal for outputting a third signal generated by amplifying the second signal in accordance with the amplification factor
Data Source
AI summary
There is provided a current measuring apparatus for measuring a first current used for estimating a load torque of the motor. The current measuring apparatus may include a detection unit configured to detect a first voltage, an amplification unit including a first input terminal at which the second signal is input, a second input terminal coupled to a first resistor and a second resistor by which an amplification factor is defined, and an output terminal for outputting a third signal, an input unit configured to input a second voltage at the first input terminal, a storage unit configured to store a third voltage an acquisition unit configured to acquire a fourth voltage, and a calculation unit configured to calculate the first current based on a difference between the third voltage and the fourth voltage.